1. Technical Field
The present invention relates to a liquid jet head that jets liquid droplets onto, and thereby record information on, recording media, a liquid jet apparatus having such a liquid jet head, and also relates to a method of manufacturing such a liquid jet head.
2. Related Art
Recently, there has been used a liquid jet head of an ink jet system that ejects ink droplets onto a recording paper or the like to record characters or figures thereon, or ejects a liquid material onto the surface of an element substrate to form a functional thin film thereon. In this technique, liquid such as ink or liquid material is guided from a liquid tank through a liquid supply tube to a channel, and is ejected in the form of liquid droplets from nozzles that communicate with the channel by applying a pressure on the liquid filling the channel. When liquid droplets are ejected, the liquid jet head and/or the recording medium is moved to record characters and/or figures, or to form a functional thin film or a three-dimensional structure each having a predetermined shape.
This kind of liquid jet head has an actuator portion having an array of a plurality of channels, which constitute a channel row, for momentarily applying a pressure on liquid; a liquid supply portion having a liquid chamber for supplying the liquid to each of the channels; a nozzle plate having an array of a plurality of nozzles that communicate with the plurality of channels, and thus jet liquid droplets. In recent years, as recording density increases, a single liquid jet head constituting a plurality of channel rows therein has been put into practical use. However, since a drive signal needs to be independently supplied to each of the channels, an increase in the number of the channel rows results in complexity in the wiring of electrodes for supplying the drive signals. When a plurality of liquid jet heads individually manufactured are arranged to constitute a plurality of channel rows, the volume of the entire liquid jet head becomes large, and at the same time, manufacturing variation makes it difficult to align the nozzle positions of the respective liquid jet heads with high accuracy.
JP 2008-68555 A describes a liquid jet head having four nozzle arrays. FIG. 10 is an exploded perspective view of a liquid jet head described in JP 2008-68555 A. The liquid jet head includes a liquid chamber unit 106, in which four nozzle arrays are formed; an actuator unit 104, in which four piezoelectric element members 142 are provided on an upper surface of a base member 141; and a frame unit 105 that incorporates the actuator unit 104 in a container portion 152, and that supplies liquid to the liquid chamber unit 106. The liquid chamber unit 106 includes a nozzle plate 101, in which the four nozzle arrays are formed in parallel; a flow path member 102, in which four arrays of liquid chambers for pressurizing liquid are formed, the flow path member 102 being bonded to the nozzle plate 101 so that the liquid chambers in each array communicates with corresponding one of the nozzles 111 in each array; and an oscillation member 103 bonded to the flow path member 102 so as to block the liquid chambers, the oscillation member 103 transmitting oscillation independently to each of the liquid chambers in each array. The four piezoelectric element members 142 of the actuator unit 104 are bonded in correspondence to the four arrays of the liquid chambers. The piezoelectric element members 142 transmit oscillation independently to each of the liquid chambers of the respective array. The frame unit 105 includes four common liquid chambers 151 that supply liquid to liquid chambers in each array.
Here, the base member 141, which holds the four piezoelectric element members 142, has a through hole 144 between the second array of piezoelectric element member 142 and the third array of piezoelectric element member 142. This through hole 144 allows flexible circuit boards (FPC cables 143) to pass therethrough. That is, the first array of piezoelectric element members 142 and the fourth array of piezoelectric element members 142 are respectively connected to two FPC cables 143 provided along outer side faces of the base member 141. The second array of piezoelectric element members 142 and the third array of the piezoelectric element members 142 are respectively connected to two FPC cables 143 that pass through the through hole 144 of the base member 141. The FPC cables 143 are respectively connected to side faces of the piezoelectric element members 142, and are each electrically connected to terminals of respective piezoelectric elements of the corresponding array.
JP 2012-6181 A describes a liquid jet head in which a first to a fourth channel rows are formed. Each of the channels includes an elongated groove formed on a surface of a piezoelectric body substrate. A drive electrode is formed on a side face of a sidewall that separates every two adjacent grooves, and a drive signal is supplied to this drive electrode to cause thickness-shear mode deformation in the sidewall, and thus a pressure is applied to liquid that fills the groove. Liquid droplets are thus ejected through a nozzle that communicates with a corresponding groove. The piezoelectric body substrates in the first and the fourth rows have the grooves formed each extending straight from the front end to the back end of the substrate. The piezoelectric body substrates in the second and the third rows have the grooves formed each starting from the front end and terminating before the back end of the substrate, and in the vicinity of the terminating point, the depth of each groove gradually decreases toward the back end of the substrate. In the piezoelectric body substrates in the first and the fourth rows, lead electrodes that are electrically connected to the drive electrodes provided on the side faces of the grooves are led out to side faces of the back ends of the piezoelectric body substrates, and are then connected to flexible circuit boards at the side faces of the back ends. In the piezoelectric body substrates in the second and the third rows, lead electrodes that are electrically connected to the drive electrodes provided on the side faces of the grooves are led out to surfaces of the substrates near the back ends of the piezoelectric body substrates, and are then connected to FPC cables at the surfaces of the substrates. The piezoelectric body substrates of the first to the fourth rows are individually manufactured, and are then bonded together by adhesive to be integrated.
The liquid jet head described in JP 2008-68555 A includes a very large number of components, and is thus complex to manufacture, which results in low productivity. For example, with respect to the piezoelectric element members 142 in the second and the third rows, which are provided facing each other across the through hole 144, it has been difficult to crimp the FPC cables 143 on the side faces on the through hole 144 side after the piezoelectric element members 142 are adhered to the base member 141. To avoid this difficulty, first the FPC cables 143 are crimped on, and connected to, the side faces of the piezoelectric element members 142, and after that, the piezoelectric element members 142 to which the FPC cables 143 are connected are bonded to the base member 141. Thus, the assembly process becomes more complicated, and alignment becomes more difficult.
The liquid jet head described in JP 2012-6181 A are manufactured in such a manner that the piezoelectric body substrates for the first to the fourth rows are individually manufactured, the piezoelectric body substrates for the second and the third rows are bonded together, the piezoelectric body substrate for the first row is bonded to the upper surface of the piezoelectric body substrate for the second row, and the piezoelectric body substrate for the fourth row is bonded to the lower surface of the piezoelectric body substrate for the third row. Thus, alignment of the grooves of the respective rows becomes complicated. Moreover, difference between the shape of the grooves of the first and the fourth rows and the shape of the grooves of the second and the third rows creates difficulty in keeping the ejection conditions of the respective rows constant.